FRACTURING APPARATUS
A fracturing apparatus in a wellbore, having a housing with at least one injection port; an injection fluid supply interface to provide injection fluid for the hydraulic fracturing apparatus; and at least one high pressure combustor received within the housing. The housing further includes a combustible medium interface that is in fluid communication with the high pressure combustor, which is configured and arranged to provide repeated ignition cycles that include a combustion cycle that ignites the combustible medium and a fuel delivery cycle that delivers the combustible medium to the combustor, wherein pressure resulting from the combustion cycle forces the injection fluid out an injection port to cause fracturing in a portion of the earth around the wellbore.
This Application claims priority to U.S. Provisional Application Ser. No. 61/664,015 titled “Apparatus & Methods Implementing a Downhole Combustor” filed on Jun. 25, 2012, which is incorporated in its entirety herein by reference.
BACKGROUNDHydraulic fracturing has become a primary method for stimulating mature reservoirs and newer shale gas/oil reserves. The benefits of fracturing post perforated wellbores is well known and this method has been able to increase productivity or access to previously non-producible reserves. These benefits, however, come with financial costs and environmental concerns. A tremendous amount of water is required during hydraulic fracturing of deep horizontal wells. Millions of gallons of water can be consumed to stimulate a single deep horizontal well. Typical costs for hydraulic fracturing include, pressurizing, pumping, and disposing of water after the job is complete.
SUMMARY OF INVENTIONThe above-mentioned problems of current systems are addressed by embodiments of the present invention and will be understood by reading and studying the following specification. The following summary is made by way of example and not by way of limitation. It is merely provided to aid the reader in understanding some of the aspects of the invention.
In one embodiment, a fracturing apparatus is provided that includes a housing, an injection fluid supply interface and at least one high pressure combustor. The housing is configured to be positioned down a wellbore. The housing has at least one injection port. The injection fluid supply interface provides injection fluid for the hydraulic fracturing apparatus. The at least one high pressure combustor is received within the housing. The housing has a combustible medium interface that is in fluid communication with the at least one high pressure combustor. The at least one high pressure combustor is configured and arranged to provide repeated ignition cycles that include a combustion cycle that ignites the combustible medium and a fuel delivery cycle that delivers the combustible medium to the combustor, wherein pressure resulting from the combustion cycle forces the injection fluid out the at least one injection port to cause fracturing in a portion of the earth around the wellbore.
In another embodiment, another fracturing apparatus is provided that includes a housing, an injection fluid supply interface, an injection fluid conduit and at least one high pressure combustor. The housing is configured to be positioned down a wellbore. The housing has a plurality of spaced injection ports. Moreover, the housing further has an injection volume holding chamber configured to hold an injection fluid volume. An injection fluid supply interface is used to provide an injection fluid for the hydraulic fracturing apparatus. The injection volume holding chamber is in fluid communication with the injection fluid supply interface. The injection fluid conduit provides a path within the housing between the injection fluid supply interface and the injection volume holding chamber of the housing. The at least one high pressure combustor is received within the housing. The housing further has a combustible medium interface that is in fluid communication with the at least one high pressure combustor. The at least one high pressure combustor is configured and arranged to provide repeated ignition cycles that include a combustion cycle that combusts the combustible medium and a fuel delivery cycle that delivers the combustible medium to the combustor, wherein pressure resulting from the combustion cycle forces the injection fluid out the at least one injection port therein causing fracturing in a portion of the earth around the wellbore.
In still another embodiment, a method of down hole fracturing is provided. The method includes: Placing a housing with at least one high pressure combustor down a wellbore; and creating oscillating pressure with the at least one high pressure combustor to cause micro fracturing in an area of the earth by the wellbore.
The present invention can be more easily understood and further advantages and uses thereof will be more readily apparent, when considered in view of the detailed description and the following figures in which:
In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize specific features relevant to the present invention. Reference characters denote like elements throughout Figures and text.
DETAILED DESCRIPTIONIn the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the inventions may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the claims and equivalents thereof.
Embodiments of the present invention provide a fracturing apparatus or apparatus for initiating and propagating fractures. Embodiments employ a down hole combustor to create oscillating pressure pulses to propagate fractures. In some embodiments, the fracturing apparatus is part of a system that includes a fuel, reactor or other fuel reformer on the surface (e.g. a catalytic partial oxidation (CPOX)), a control system for delivery of fuel and downhole oxidizer and an ignition source. A fuel, such as but not limited to, natural gas, propane, methane, diesel would be run through the reactor so that the end constituents would be gaseous and predictably combustible in the downhole environment. This allows production of a synthetic fuel including mostly gaseous CO, H2 and simple hydrocarbons for highly efficient and stable combustion. Gaseous fuels will improve mixing with a gaseous oxidizer, such as air and enable surface processing of various fuels for delivery to the fracturing apparatus 100. The fracturing apparatus 100 may be used in a wellbore (not shown) in an earth formation (not shown).
Referring to
Enclosed within housing 102 of the embodiment of
A combustor 200 (such as ignition system 200 described below in relation to
Referring to
Piston 404 subdivides the cylinder into two chambers, a primary combustion chamber 412 and a secondary combustion chamber 414. Piston 404 is slidably disposed within the primary combustion chamber 412 and during an injection stroke may slidaby move to secondary combustion chamber 414. The primary combustion chamber 412 defines a first compression stage and the secondary combustion chamber 414 defines the second compression stage. Primary combustion chamber 412 and secondary combustion chamber 414 may be adjacent to one another and may be of the same size or different sizes. The two chambers may be in communication, by way of conduits and control valves (not shown). Each combustion chamber has its own ignition system 200.
At one end of housing 402 are included inlet ports or injection fluid supply interface 416. The inlet ports 416 provide air, fuel (combustible medium) and fracture liquid which can include water and propellants plus a number of chemical additives, as well as a connection or port (not shown) to deliver power to ignition system 200. At an end opposite of inlet ports 416 are injection or exhaust ports 418. Injection or exhaust ports 418 are configured to have one-way flow control valves 420. In an embodiment, the downhole fracturing apparatus 400 has a passive control system that utilizes a positive pressure differential to inject gases into primary combustion chamber 412.
Referring to
The pressure and the fuel to air ratio in the primary combustion chamber 506, as well as the area ratio that exist in the fracturing apparatus, are set based on wellbore conditions so that the work performed on the piston cools the combustion gases sufficiently for injection into the wellbore. Warm post combustion gases are vented into the reservoir 507 via the outlet ports 504. The expansion of the primary combustion chamber 506, due to combustion, pressurizes the hydraulic or injection fluid. On the pressurization stroke, the piston 502 will force the fluids into the reservoir 507 under high pressure. Check valves are used to control the direction of the flow.
A low pressure chamber 509 (1 atm) opposing the injection volume maintains a differential force that acts to compress the primary combustion chamber 506 once all the available work is extracted. During the start of the return stroke, the primary combustion chamber 506 is compressed and fracturing fluid (injection fluid) is drawn into the injection volume 511. This compression of the primary combustion chamber 506 drives spent air and fuel (effluent) out of the exhaust ports 512 of a secondary chamber 508. The return stroke is initiated by the low pressure chamber and in some cases by a compressed spring (not shown) which increases the volume of the secondary combustion chamber 508 thus pulling fresh fuel and air (or another oxidant) 516 into the chamber which will be ignited driving the piston back to its initial position. Upon ignition, the secondary chamber 508 pressurizes. The combination of forces acting on the pistons compresses a coiled spring (not shown) in the primary combustion chamber. The same cooling and venting scheme is applied to the secondary combustion chamber. Upon venting sufficient gas pressure from the secondary chamber, the spring in the primary chamber returns to its initial state, retracting piston. The expansion of the primary combustion chamber 506 creates suction. This will draw fuel and air into the primary combustion chamber 506. Once the primary combustion chamber is sufficiently filled, the ignition system causes another combustion wave to pressurize the primary combustion chamber and the process repeats.
The housing 402 has outlets that vent the combined hydraulic fluids and combustion byproducts into the formation. This cycle is repeated with the net effect being a controlled pressurization of the wellbore that utilizes the high pressure/moderate temperature gas from the combustion process and wellbore fluid drawn from the formation to hydraulically fracture the formation. In one embodiment high pressure combustion is performed at 6000 psi. In another embodiment, the wellbore pressure may be or about 5500 to 6000 psi with delivered pressures of 5900 psi to 6400 respectively.
The above described fracturing tools generate a warm high gas content foam that is greater than 50% gas by volume from a combination of hot exhaust gas from the combustor and the injection fluid near the wellbore to initiate micro fracturing. In another embodiment, a low gas content foam is created by adjusting the air-fuel and liquid supply. Moreover, this foam will convert to a low gas content foam by condensation and the cooling of the hot exhaust gas that has high bulk molecules to support fractures deeper into the formation as the foam gets further away from the fracturing apparatus.
In other embodiments, the fracturing tools 100 or 400 may be augmented with known solid propellant systems. By combining the fracturing tools 100 or 400 with a propellant system, pressure profiles may be tailored to the desired wellbore conditions. Combining of the two systems also provide for sustained pressures as compared to known systems (e.g. gas guns) that provide for single pressure pulses. In one embodiment, the combined system or the disclosed systems may be used to effectively apply Paris' law for fatigue crack growth. Paris' law has traditionally been used to determine a rate of crack growth as a component (e.g. a reservoir or wellbore) is subjected to repetitive fatigue conditions. In other words, as a reservoir or wellbore is subjected to repetitive or cyclic fatigues, or forces, such as a repetitive or cyclic pressure, a crack can develop in the reservoir or wellbore.
Paris' law can be described mathematically as da/dN=C(ΔK)m where a is the half crack length, N is the number of fatigue cycles, da/dN is the rate of change of the half crack length with respect to the number of fatigue cycles, C is a material constant of the crack growth equation and a crack geometry, and m is an exponent that may be selected based on the material type to be analyzed. ΔK is the range of a stress intensity factor K, where K may be based on a loading state.
The ignition system and combuster 200 described above is illustrated in
As discussed above, the jet extender 210 extends from a central passage of a fuel injector plate 217. As
The fuel inlet tube 206 provides fuel to the combustor 200. In particular, as illustrated in
Referring to
Air under pressure is also delivered to the combustor 200 through passages in the housing 102. In this embodiment, air under pressure is between the injector body 202 and the housing 102. Air further passes through air passages 207 in the air swirl plate 208 therein providing an air flow for the main combustion chamber 300. As illustrated, some of the air enters the premix air inlet 204 and is delivered to the premix chamber 212. The air and the fuel mixed in the premix chamber 212 are passed on to the air/fuel premix injector 214 which is configured and arranged to deliver the air/fuel mixture so that the air/fuel mixture from the air/fuel premix injector 214 swirls around in the initial ignition chamber 240 at a relatively low velocity. One or more glow plugs 230a and 230b heat this relatively low velocity air/fuel mixture to an auto-ignition temperature wherein ignition occurs. The combustion in the initial ignition chamber 240 passing through the jet extender 210 ignites the air/fuel flow from the fuel injector plate 217 and the air swirl plate 208 in the main combustion chamber 300. Once combustion has been achieved in the main combustion chamber 300, power to the glow plugs 230a and 230b is discontinued. Hence, combustion in the initial ignition chamber 240 is a transient event so that the heat generated will not melt the components. The period of time the glow plugs 230a and 230b are activated to ignite the air/fuel mix in the initial ignition cavity 240 can be brief. In one embodiment it is around 8 to 10 seconds.
In an embodiment, an air/fuel equivalence ratio in the range of 0.5 to 2.0 is achieved in the initial ignition chamber 240 via the air/fuel premix injector 214 during initial ignition. Concurrently, the air/fuel equivalence ratio in the main combustion chamber 300 is in the range of 0.04 to 0.25, achieved by the air swirl plate 208 and the fuel injector plate 217. After ignition of the flow in the initial combustion chamber 240 and the main combustion chamber 300, the glow plugs 230a and 230b are shut down. An air/fuel equivalence ratio within a range of 5.0 to 25.0 is then achieved within the initial ignition chamber 240, while concurrently, an air/fuel equivalence ratio in the range of 0.1 to 3.0 is achieved in the main combustion chamber 300, by the air swirl plate 208 and the fuel injector plate 217. This arrangement allows for a transient burst from the initial ignition chamber 240 to light the air/fuel in the main chamber 300, after which any combustion in the initial ignition chamber 240 is extinguished by achieving an air/fuel equivalence ratio too fuel rich to support continuous combustion. To cease combustion in the main combustion chamber 300 either or both the air and the fuel is shut off to the combustor 200.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.
Claims
1. A fracturing apparatus comprising:
- a housing configured to be positioned down a wellbore, the housing having at least one injection port;
- an injection fluid supply interface to provide injection fluid for the hydraulic fracturing apparatus; and
- at least one high pressure combustor received within the housing, the housing having a combustible medium interface that is in fluid communication with the at least one high pressure combustor, the at least one high pressure combustor configured and arranged to provide repeated ignition cycles that include a combustion cycle that ignites the combustible medium and a fuel delivery cycle that delivers the combustible medium to the combustor, wherein pressure resulting from the combustion cycle forces the injection fluid out the at least one injection port to cause fracturing in a portion of the earth around the wellbore.
2. The fracturing apparatus of claim 1, wherein the at least one port is a plurality of spaced injection ports positioned around a cylindrical side portion of the housing.
3. The fracturing apparatus of claim 1, further comprising;
- a flow control valve selectively covering the at least one injection port, the low control valve configured to uncover the at least one injection port when a select amount of pressure is applied to the flow control valve.
4. The fracturing apparatus of claim 1, further comprising:
- the housing including an injection volume holding chamber configured to hold an injection fluid volume prior to a combustion cycle.
5. The fracturing apparatus of claim 3, further comprising:
- an injection fluid conduit providing a path within the housing between the injection fluid supply interface and the injection volume holding chamber of the housing.
6. The fracturing apparatus of claim 3, further comprising:
- a combustion tube terminating in a venturi, the at least one high pressure combustor positioned to direct exhaust gas from the combustion cycle into the combustion tube and out the venturi into the injection fluid in the injection volume holding chamber.
7. The fracturing apparatus of claim 1, further comprising:
- a piston assembly received within the housing, the piston assembly configured to apply pressure to the injection fluid in response to the combustion cycle.
8. The fracturing apparatus of claim 7, the piston assembly including:
- a combustion piston head;
- a injection fluid piston head; and
- a connection shaft having a first end coupled to the combustion piston and a second end coupled to the injection fluid piston head.
9. The fracturing apparatus of claim 8, further comprising:
- the housing including a primary combustion chamber and a secondary combustion chamber, the combustion piston movably received within the primary and secondary combustion chambers, the combustion piston further at least in part defining the primary and secondary combustion chambers;
- the at least one high pressure combustor including a primary high pressure combustor positioned to combust combustible medium in the primary chamber and a secondary combustor position of combust the combustible medium in the secondary chamber; and
- the injection fluid piston head positioned in an injection volume holding chamber in the housing, the piston assembly configured and arranged so that ignition of the primary high pressure combustor causes the injection fluid piston head to push the injection fluid out of the injection volume holding chamber and the ignition of the secondary combustion chamber causes the injection fluid piston head to draw more injection fluid into the injection volume holding chamber.
10. The fracturing apparatus of claim 9, the housing having a low pressure chamber positioned between the secondary combustion chamber and the injection volume holding chamber.
11. A fracturing apparatus comprising:
- a housing configured to be positioned down a wellbore, the housing having a plurality of spaced injection ports, the housing further having an injection volume holding chamber configured to hold an injection fluid volume;
- an injection fluid supply interface to provide injection fluid for the hydraulic fracturing apparatus, the injection volume holding chamber being in fluid communication with the injection fluid supply interface;
- an injection fluid conduit providing a path within the housing between the injection fluid supply interface and the injection volume holding chamber of the housing; and
- at least one high pressure combustor received within the housing, the housing further having a combustible medium interface that is in fluid communication with the at least one high pressure combustor, the at least one high pressure combustor configured and arranged to provide repeated ignition cycles that include a combustion cycle that combusts the combustible medium and a fuel delivery cycle that delivers the combustible medium to the combustor, wherein pressure resulting from the combustion cycle forces the injection fluid out the at least one injection port therein causing fracturing in a portion of the earth around the wellbore.
12. The fracturing apparatus of claim 11, further comprising;
- a flow control valve selectively covering the at least one injection port, the low control valve configured to uncover the at least one injection port when a select amount of pressure is applied to the flow control valve.
13. The fracturing apparatus of claim 11, further comprising:
- a combustion tube terminating in a venturi, the at least one high pressure combustor positioned to direct exhaust gas from the combustion cycle into the combustion tube and out the venturi into the injection fluid in the injection volume holding chamber.
14. The fracturing apparatus of claim 11, further comprising:
- a piston assembly received within the housing, the piston assembly configured to apply pressure to the injection fluid in response to the combustion cycle.
15. The fracturing apparatus of claim 14, the piston assembly including:
- a combustion piston head;
- a injection fluid piston head;
- a connection shaft having a first end coupled to the combustion piston and a second end coupled to the injection fluid piston head;
- the housing including a primary combustion chamber and a secondary combustion chamber, the combustion piston movably received within the primary and secondary combustion chambers, the combustion piston further at least in part defining the primary and secondary combustion chambers;
- the at least one high pressure combustor including a primary high pressure combustor positioned to combust combustible medium in the primary chamber and a secondary combustor position of combust the combustible medium in the secondary chamber; and
- the injection fluid piston head positioned in an injection volume holding chamber in the housing, the piston assembly configured and arranged so that ignition of the primary high pressure combustor causes the injection fluid piston head to push the injection fluid out of the injection volume holding chamber and the ignition of the secondary combustion chamber causes the injection fluid piston head to draw more injection fluid into the injection volume holding chamber.
16. A method of down hole fracturing, the method comprising:
- placing a housing with at least one high pressure combustor down a wellbore; and
- creating oscillating pressure with the at least one high pressure combustor to cause micro fracturing in an area of the earth by the wellbore.
17. The method of claim 16, further comprising:
- forcing injection fluid out the housing through a plurality of injection ports.
18. The method of claim 17, further comprising:
- generating a warm high content foam that is greater than 50% gas by volume from a combination of hot exhaust gas from the combustor and the injection fluid near the wellbore to initiate micro fracturing.
19. The method of claim 18, further comprising:
- using low gas content foam formed by condensation and the cooling of the hot exhaust gas with high bulk molecules to support fractures deeper into the formation.
20. The method of claim 16, further comprising:
- augmenting the oscillating pressure generated by the at least one down hole combustor with a solid propellant.
Type: Application
Filed: Mar 15, 2013
Publication Date: Dec 26, 2013
Patent Grant number: 9383094
Inventors: Joseph A. Alifano (Commack, NY), Daniel Tilmont (Rocky Point, NY)
Application Number: 13/840,672
International Classification: E21B 43/263 (20060101);